FIELD OF THE INVENTION
This invention relates to a liquid crystal display device in which a flexible printed circuit board is thermally pressure-contacted to a liquid crystal display panel through an electrically anisotropic film, and to a method of making the same.
A liquid crystal display device is thin in thickness and light in weight so that it has been widely used for various small-size, hand-held-type data processing equipment. As shown in FIG. 7, a liquid crystal device includes a liquid crystal display panel 16 which consists of a circuit array substrate 11, a counter substrate 12 provided opposite to the array substrate 11 and a liquid crystal material (not shown) located between the array and counter substrates 11 and 12. On the array substrate 11, scanning and signal lines (not shown) are disposed to cross each other at a right angle, and pixel electrodes and switching circuits to supply video signals to the electrodes are provided in the vicinities of the cross points of the scanning and signal lines. The scanning and signal lines are coupled to electrically connecting terminals 15 at an edge portion of the array substrate 11 in order to supply signals to, and to derive signals from, the liquid crystal display panel 16. A common electrode is provided on the counter electrode 12. Polarizers 13 and 14 are attached to outer surfaces of the array and counter substrates 11 and 12, respectively. In a driver-monolithic-type liquid crystal display panel, however, driver circuits are disposed at surrounding areas of an image forming region in the array substrate.
A flexible printed circuit board ("FPC") 61 consists of a base film 1, an adhesive layer 2 applied on the base film 1, a printed signal line layer 3 made of copper foil along a surface of the layer 2, and a protective film 4 to protect the signal line layer 3. An electrically anisotropic conductive film ("ACF") 52 is provided to connect the terminals 15 to the FPC 61. The ACF 52 is made of a thermosetting isolation layer and electrically conductive particles dispersed in the isolation layer. The signal line layer 3 is thermally pressure-contacted to the terminals 15 through the ACF 52 at the edge portion of the array substrate 11.
Since the array substrate 11 has a sharp edge 50 as shown in FIG. 5, the signal line layer 3 of the FPC 61 is often broken by the edge 50 during their assembling process. To avoid this, an additional process is required to cut it out to form a slope 51 as shown in FIG. 6.
Since the signal line 3 is not entirely covered with the protective film 4, it may be still damaged during the assembling process.